Burner for a boiler



y 1965 e. 1'. MITCHELL ETAL 3,185,202

BURNER FOR A BOILER Filed May 10, 1963 2 Sheets-Sheet 1 FIG.\

ATTORNEY May 25 1965 G. T. MITCHELL ET AL 3, 5,202

BURNER FOR A BOILER Filed May 10, 1963 2 Sheets-Sheet 2 33 F 16. 5 F166INVENTORS GERALD T. MITCHELL.

B RICHARD CUNN] GHA R. Jib-M ATTOR NEY United States Patent 3,185,202BURNER FOR A BOILER Gerald T. Mitchell, Wilmette, Ill., and RichardCunningham, (in, Houston, Tex., assignors to Vapor Corporation, Chicago,Ill., a corporation of Delaware Filed May 10, 1963, Ser. No. 279,463 7Claims. (Cl. 158-4) This invention relates in general to a burner for aboiler or a steam generator, wherein the burner provides the heat sourcethat is capable of furnishing the hot gases necessary to produce theoutput of the boiler or steam generator.

The burner of the present invention comprises a fire pot composed of arefractory lined metal can or body having a plurality ofcircumferentially spaced combustion throats. A burner nozzle is mountedat each throat and arranged to direct its spray pattern across the spraypattern of an adjacent burner nozzle. Each combustion throat isconstructed to give the maximum pressure drop possible with availablecombustion air. A plenum chamber surrounds the fire pot and ispressurized for supplying the combustion air to the combustion throats.The structure of the fire pot, the nozzles and their arrangement, andthe plenum chamber are such that nearly stoichiometric combustion isachieved. The present invention is especially useful in the burning ofheavy grade fuel oils so completely that no smoke is visible.

It is an object of the present invention to provide a new and improvedburner for boilers or steam generators.

Another object of this invention is in the provision of a burner forboilers or steam generators, wherein the construction of the burner iscompact and much smaller than other burners of comparable heat output.

Still another object of this invention resides in the provision of aburner for boilers or steam generators that is capable of burning heavygrade fuel oils completely with no visible smoke.

A further object of this invention is to provide a burner for boilers orsteam generators that includes a fire pot having a plurality of burnernozzles, wherein each burner nozzle is arranged to direct its spraypattern across the spray pattern of an adjacent nozzle so that morecomplete combustion can be obtained.

A still further object of this invention is in the provision of a burnerfor boilers or steam generators including a fire pot having a pluralityof combustion throats and a burner associated with each combustionthroat, and a plenum chamber in surrounding relation with the fire pot,wherein the plenum chamber is pressurized to supply the combustion airto the combustion throats.

Another object of this invention resides in the provision of a burnerfor boilers or steam generators, wherein the burner includes a fire pothaving a plurality of combustion throats that are constructed to givethe maximum pressure drop possible with available combustion air.

A still further object of this invention is to provide a burner forboilers or steam generators that includes a fire pot having a pluralityof burner nozzles, wherein at least one of the nozzles may be shut offfor removal and cleaning without necessitating the shutting down of theburner.

Other objects, features, and advantages of the invention will beapparent from the following detailed disclosure, taken in conjunctionwith the accompanying "ice sheets of drawings, wherein like referencenumerals refer to like parts, in which:

FIG. 1 is a front elevational view of the burner and associated elementsin accordance with the present invention;'

FIG. 2 is a vertical sectional view taken substantially along line 22 ofFIG. 1;

FIG. 3 is a transverse sectional view of the fire pot takensubstantially along line 3-3 of FIG. 2;

7 FIG. 4 is a diagrammatic view showing the fire pot in cross sectionand the spray patterns of the burner nozzles;

FIG. 5 is a top plan view of the fuel nozzle employed in the presentinvention; and

FIG. 6 is a transverse sectional view taken substantially along line 6-6of FIG. 5.

Referring now to the drawings and particularly to FIG. 2, the burner ofthe present invention includes generaly a fire pot 10 enclosed by ahousing 11 defining with the fire pot a pressurized plenum chamber 12,and a plurality of burner nozzles 13.

The fire pot 10 generally comprises a refractory lined metal can andincludes particularly a cylindrically-shaped body 14 closed at one endby a dome-shaped cover 15, and having a choke 16 at the other endthrough which the hot gases are discharged from the fire pot and to thecoils of a boiler or steam generator. The cover 15 is mounted on thebody 10 by means of a plurality of stud bolts 17 welded or otherwisesuitably secured to the body 10, and a bracket 18 welded or otherwisesecured to the cover 15 and having holes for receiving the stud bolts17. Nuts 19 are threadedly received on the stud bolts 17 to bear againsteach bracket 18 and hold the cover in place. A ceramic or otherwise hightemperature gasket 20 is preferably arranged between the cover 15 andthe body 10.

A plurality of combustion throats 21 are circumferentially and equallyspaced in the body 14 of the fire pot 10, each of which has associatedtherewith a burner nozzle 13. The longitudinal axis of each combustionthroat, as represented generally by the line 22, (FIG. 3) is coaxialwith the longitudinal axis of each associated burner nozzle and thisaxis is angularly displaced about 30 from a radial line 23 projectingfrom the longitudinal axis of the fire pot and intersecting the axis ofthe throat at the inner wall 24a of the fire pot. Each combustion throatis venturi-shaped to provide the maximum pressure drop possible with theavailable combustion air. The inner and outer ends of each combustionthroat are flared. The throat diameters are flared open at 50 at theinside surface of the combustion chamber, wherein the angle is measuredfrom the nozzle tip as illustrated particularly in FIG. 3.

The throat diameter depends primarily on the combustion air staticpressure available. While six combustion throats and associated nozzlesare shown in the illustrated embodiment, it should be appreciated that agreater or smaller number of throats and nozzles may be employeddepending upon the power output desired from the burner. As can be seenparticularly in the diagrammatic view of FIG. 4, the combustion throatsand nozzles are arranged so that the spray pattern of one nozzle crossesthe spray pattern of an adjacent nozzle and is directed at the alternateadjacent nozzle.

The fire pot defines therein a combustion chamber 24 within which theair and fuel mixture is burned, and thereafter the resultant gasesdischarged through the choke 16. The length of the choke 16 isapproximately 40 percent of the total length of the combustion chamher,while the diameter of the choke is determined by the inside diameter ofthe boiler coils. In the embodiment illustrated, any two burner nozzles[13 may be turned off, removed for cleaning and/or servicing withoutsubstantially affecting the combustion characteristics of the burner,thereby eliminating the necessity of shutting down the boiler whileservicing the burner.

A blower 25, FIG. 1, is mounted laterally of the housing 11 andcommunicates with the plenum chamber 12 by means of a duct 26 for thepurpose of supplying the combustion air to the plenum chamber 12 and thefire pot 10. The air delivered from the blower wipes across the outerwalls of the fire pot 10, and is thereby preheated prior to enteringthe'combustion throats 21.

The burner nozzles 13, when delivering light or heavy fuel oils, atomizethe oil by means of steam, air or fuel pressure. The combustion airsupplied to the nozzle area and through the combustion throats 21 mixeswith the atomized fuel as it is sprayed from the burner nozzles. Theparticular nozzle direction produces a swirling and turbulent mixingaction within the combustion chamber which aids in the completion of thecombustion process. Moreover, the combustion air is directed within thecombustion chamber in such a manner that no fuel impinges upon the innerwalls of the combustion chamber, and the fuel-air ratio is relativelyuniform throughout the combustion chamber. The combustion throats 21 arelocated quite close to the closed end of the combustion chamber as notedparticularly in FIG. 2.

An opening 27 is provided in the center of the domeshaped cover 15, andeffectively in the top of the combus tion chamber for the purpose ofcreating air movement around the cover and to provide a cooling actionfor the plenum chamber dome.

An air curtain is formed along the inside refractory walls of thecombustion chamber by providing a plurality of circumferentiallyarranged holes 28 extending from the inner end wall 29 to the outersurface of the outer wall 30 as seen in FIGS. 2 and 3. The holes 28extend parallel to the longitudinal axis of the fire pot and'arearranged to form the curtain of air along the inner refractorycombustion wall Zea by the fact that the holes are positioned to havetheir outlets directly along the inner Wall 24a. The air curtainprovides a lowering of the refractory side wall temperatures.

The heavy oil normally employed as fuel for the burner nozzles ispreferably preheated to a range of 120-300 F. depending upon theviscosity of the particular oil being burned. A higher temperature isrequired for atomization where the viscosity is higher. Further, asheretofore mentioned, the combustion air moving through the plenumchamber 12 is preheated as it travels between the plenum chamber and thecombustion chamber 24.

The relative dimensions of the fire pot are important for providingstoichiometric combustion. An example of relative dimensions compriseshaving an inside combustion chamber diameter of 26%. inches, a totalcombustion chamber depth as meatured from the end wall 29 to the deepestpoint along the inside surface of the domeshaped cover 15 of 22 inches,the concave dome also having a 26% inch inside diameter and with a'depthof 4 inches at the center, the choke diameter being 14 inches and thechoke depth being 11 inches. The hole 27 in the cover 15 is 1 inch indiameter, while the holes 28 are inch in diameter. There are providedeighteen holes 28 which are circumferentially and equally spaced at thechoke end of the combustion chamber. Further, as heretofore mentioned,the choke length is approximately 40 percent of the total length of thecombustion chamber as measured from the choke surface edge to the insidetop of the dome cover 15. With a fire pot having the above relativedimensions, test results indicated a good fire which approachedstoichiometric combustion of:

Smoke reading 1. Blower air pressure 8.3 inch water.

A six hole burner nozzle is employed to atomize the oil fed through thecombustion throat, as illustrated in FIGS. 5 and 6, and generallyindicated by the numeral 31. The nozzle includes six mixing orifices 32having an included angle of 50, and opening through an inclined surface33 that is set 25 from the horizontal or from the transverse axis ofsaid nozzle. An air inlet 34 is provided at the inlet end 35 whichcommunicates with the mixing orifices 32 through atomizing air holes 36.An annular oil inlet groove 37 is arranged at the inlet end 35 of thenozzle and communicates .with the mixing orifices 32 by means of fueloil holes having an inlet end 38 necked down to an outlet end 39. Theaxis of the oil holes is offset 20 from the vertical and 45 from theaxis of the mixing orifices 32. The mixing orifices 32 and the inletends 38 of the oil holes are inch in diameter, while the atomizing airholes 36 and the necked down portion of the oil holes 39 are No. 70drill. As seen in FIG. 3, a hole 40 is provided for a pilot.

The fire pot of the present invention with the nozzle arrangement asabove identified eliminates the formation of carbon deposits on therefractory side walls and any substantial carbon build up on thecombustion throat.

From the foregoing, it is seen that the present invention provides animproved burner for boilers capable of burning heavy fuel oils whileproviding substantially stoichiometric combustion, having greater outputwith smaller size, and capable of being serviced without being shutdown.

It will be understood that modifications and variations may be effectedwithout departing from the scope of the novel concepts of the presentinvention, but it is understood that this application is to be limitedonly by the scope of the appended claims.

The invention is hereby claimed as follows:

1. A burner for a boiler comprising, a fire pot having a cylindricalbody defining a combustion chamber, a domeshaped end wall closing oneend of said body and a choke at the other end of said body, a pluralityof combustion throats having inner and outer ends and beingcircumferentially and equally spaced around said body along a singletransverse plane spaced closely. adjacent to said end wall, and a burnernozzle for each throat, the longitudinal axis of each burner nozzle andeach throat being coaxial and being angularly displaced from a radialline projecting from the longitudinal axis of the fire pot andintersecting the axis of the associated throat and burner nozzle at theinner wall of the fire pot so that each burner nozzle is arranged todirect its spray pattern across the spray pattern of an adjacent spraynozzle, means positively delivering combustion air through said throats,and means for providing an air curtain along the inside walls of saidbody to cool same, said air curtain means including a plurality of holesextending through said body at the choke end thereof and being parallelto the longitudinal axis of said body, said holes opening adjacent tothe inside walls of the body.

2. The combination as defined in claim 1, wherein the a length of thechoke is equal to about 40% of the total length of the combustionchamber.

3. The combination as defined in claim 1, wherein said throats areflared open 50 at the inside surface of the combustion chamber.

4. The combination as defined in claim 1, wherein the inner and outerends of said throats are flared.

5. The combination as defined in claim 1 wherein said 1,924,878 8/33Parry 11028 dome-shaped end wall is provided with an opening in the2,242,797 5/41 Lucke 15 8-1.5 center and is in communication with saidcombustion air 2,893,646 6/59 Batts 239-419 delivery means for creatingair movement around the end 2,917,011 12 59 Komer 110 23 wall to providea cooling action therefor. 5 2,9 5,205 5 1 Boelsma 158-4 6. Thecombination as defined in claim 1, wherein said 9 701 6/62, -H 1 239-419combustion throats are venturi-shaped. 3,105,540 10/63 Hardgrove 1 7.The combination as defined in claim 1, wherein each burner nozzle isangularly displaced about from said FOREIGN A NT adlal 10 218,657 12/61Austria.

References Cited by the Examiner UNITED STATES PATENTS 1,777,411 10/30Mayr l58--l JAMES W. WESTHAVER, Primary Examiner.

MEYER PERLIN, Examiner.

1. A BURNER FOR A BOILER COMPRISING, A FIRE POT HAVING A CYLINDRICALBODY DEFINING A COMBUSTION CHAMBER, A DOMESHAPED END WALL CLOSING ONEEND OF SAID BODY AND A CHOKE AT THE OTHER END OF SAID BODY, A PLURALITYOF COMBUSTION THROAT HAVING INNER AND OUTER ENDS AND BEINGCIRCUMFERENTIALLY AND EQUALLY SPACED AROUND SAID BODY ALONG A SINGLETRANSVERSE PLANE SPACED CLOSELY ADJACENT TO SAID END WALL, AND A BURNERNOZZLE FOR EACH THROAT, THE LONGITUDINAL AXIS OF EACH BURNER NOZZLE ANDEACH THROAT BEING COAXIAL AND BEING ANGULARLY DISPLACED FROM A RADIALLINE PROJECTING FROM THE LONGITUDINAL AXIS OF THE FIRE POT ANDINTERSECTING THE AXIS OF THE ASSOCIATED THROAT AND BURNER NOZZLE AT THEINNER WALL OF THE FIRE POT SO THAT EACH BURNER NOZZLE IS ARRANGED TODIRECT ITS SPRAY NOZZLE, ACROSS THE SPRAY PATTERN OF AN ADJACENT SPRAYNOZZLE, MEANS POSITIVELY DELIVERING COMBUSTION AIR THROUGH SAID THROATS,AND MEANS FOR PROVIDING AN AIR CURTAIN ALONG THE INSIDE WALLS OF SAIDBODY TO COOL SAME, SAID AIR CURTAIN MEANS INCLUDING A PLURALITY OF HOLESEXTENDING THROUGH SAID BODY AT THE CHOKE END THEREOF AND BEING PARALLELTO THE LONGITUDINAL AXIS OF SAID BODY, SAID HOLES OPENING ADJACENT TOTHE INSIDE WALLS OF THE BODY.